Previously, many types of pop-up sprinklers have been used to provide an effective means for producing an even distribution of water over a large area by popping-up from the ground surface, spraying the turf and retracting automatically after use. Pop-up sprinklers have been in use for decades, allowing lawns and turf to be automatically irrigated and machine mowed without the necessity of manually adjusting or removing the sprinklers. In most cases, the sprinklers are hydraulically-actuated to achieve the upwardly extending movement and many types of seals have been employed to prevent clogging and increase reliability.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention, however the following U.S. patents are considered related:
______________________________________ U.S. PAT. NO. INVENTOR ISSUED ______________________________________ 5,423,486 Hunter 13 June 1995 5,368,229 Hayes, et al 29 Nov. 1994 5,123,597 Bendall 23 June 1992 5,104,090 Grizzle, et al 14 April 1992 4,886,209 Dawn 12 Dec. 1989 4,834,289 Hunter 30 May 1989 4,796,809 Hunter 10 Jan. 1989 4,316,579 Ray et al 23 Feb. 1982 4,244,555 Maggioni, et al 13 Jan. 1981 3,921,910 Hayes, et al 25 Nov. 1975 ______________________________________
U.S. Pat. No. 5,423,486 issued to Hunter is for a pop-up sprinkler unit that includes a floating sleeve of grit resistant material. The sleeve is reciprocally mounted between the inner and outer housings for deflecting grit when the sleeve is retracted.
U.S. Pat. No. 5,123,597 of Bendall teaches a sprinkler nozzle with a curved outlet section to enhance the reach of the nozzle while maintaining a coherent or homogenous water stream.
U.S. Pat. No.4,886,209 invented by Dawn discloses a sprinkler with a pop-up stem and a valve cover blocking the opening to the stem. A resiliently deformable valve element is loosely mounted to enable particulate material to be moved in a planar direction.
Patent of Hunter issued under U.S. Pat. No. 4,796,809 described a two-stage pop-up sprinkler that employs a cylindrical housing and a telescoping sleeve reciprocally mounted on the sleeve. An inner sleeve contains the sprinkler head and driving mechanism. The first sleeve extends primarily from the housing for ground clearance then the second sleeve expands upwardly permitting water to be distributed.
U.S. Pat. No 3,921,910 issued to Hayes, et al teaches a pop-up sprinkler with an annular seal providing a static seal, spring seat and pressure responsive leakage path to remove debris during extended movement of the sprinkler head. The annular seal also provides a seal when the head is extended and delivers a wiping action when the head is retracted.
For background purposes and as indicative of the art to which the invention relates reference may be made to the patents issued to Hayes, et al, Grizzle et al, Hunter, Ray, et al, and Maggioni, et al.